Rapidly progressive steroid-resistant focal segmental glomerulosclerosis associated with an INF2 exon 6 variant.

Variants in the inverted formin-2 (INF2) gene are a known cause of hereditary focal segmental glomerulosclerosis (FSGS) and Charcot-Marie-Tooth disease. We report a case of rapidly progressive FSGS associated with a rare INF2 variant. A 12-year-old boy developed proteinuria and was diagnosed with FSGS at age 14 following a renal biopsy. Steroid therapy and subsequent immunosuppressive treatments, including plasma exchange, were ineffective. At age 15, a heterozygous missense variant in exon 6 of the INF2 gene (c.763G>A, p.Asp255Asn) was identified. Despite conservative management, the patient progressed to end-stage kidney disease at age 17. Although exon 6 variants are rarely reported, the present case showed a relatively aggressive renal course.